When driving along a winding road, eye movements and steering are tightly linked. When approaching a bend, the driver looks across to the inside kerb (the tangent point) some time before turning the steering wheel. All drivers we have tested show this optimal coordination, without which driving is impaired. An intriguing question is how much of the benefit for steering arises just from moving the eyes in this coordinated way (ahead of steering and in the same direction), and how much from the visual information that the eyes move to acquire, in this instance the foveated tangent point. This can be answered by dissociating the two, by reducing visibility of the road ahead (and crucially of the tangent point) to a level at which drivers might or might not choose to move their eyes but, if they do, will not gain the information they seek. Twenty subjects repeatedly drove a simulated stage of the World Rally Championship. With full visibility, they exhibited the usual coordination of eye movements and steering. Subsequently, visibility was reduced on the left hand side. Drivers who persisted in making eye movements coordinated with steering to the left, despite the fact that they could no longer see the tangent point on that side, performed better than drivers who under the identical conditions did not look to the left. This confirms that the making of coordinated eye movements itself benefits steering, even when the eye movements do not yield the visual information sought.

When driving along a winding road, eye movements and steering are tightly linked; the driver looks across to the inside kerb of an approaching bend some time before turning the steering wheel. With the eyes leading, the oculomotor controller assists the neural centres controlling steering; prevention of any eye movements correlated with steering impairs driving, so the coordination is crucial for safety. A key question is therefore what are the limits of acceptable variation in timing and degree of coordination. Over a period of continuous driving on the open road, how much does the relative timing and degree of coordination between eye and steering movements vary? A related question is how brief a period of driving will suffice to measure these coordination parameters. Drivers' eye movements and steering were measured over different time periods ranging from 15 s to 6 min epochs of natural driving along a winding country road to establish the variability in coordination and the minimum time period required to characterise it. We show here that brief periods of driving, 30 s or less, are inadequate for describing eye-steering coordination. But a minute of driving yields an accurate description much of the time; and 2 min is sufficient both to accurately describe this relationship and to show that it is highly consistent for a given individual, and for different people driving the same route.

We tested some of the key predictions of processing efficiency theory using a simulated rally driving task. Two groups of participants were classified as either dispositionally high or low anxious based on trait anxiety scores and trained on a simulated driving task. Participants then raced individually on two similar courses under counterbalanced experimental conditions designed to manipulate the level of anxiety experienced. The effort exerted on the driving tasks was assessed though self-report (RSME), psychophysiological measures (pupil dilation) and visual gaze data. Efficiency was measured in terms of efficiency of visual processing (search rate) and driving control (variability of wheel and accelerator pedal) indices. Driving performance was measured as the time taken to complete the course. As predicted, increased anxiety had a negative effect on processing efficiency as indexed by the self-report, pupillary response and variability of gaze data. Predicted differences due to dispositional levels of anxiety were also found in the driving control and effort data. Although both groups of drivers performed worse under the threatening condition, the performance of the high trait anxious individuals was affected to a greater extent by the anxiety manipulation than the performance of the low trait anxious drivers. The findings suggest that processing efficiency theory holds promise as a theoretical framework for examining the relationship between anxiety and performance in sport.

On a winding open road, a driver consistently looks to the inside of each bend before turning the steering wheel. When researchers disrupt this coordination by instructing drivers not to move their eyes, drivers' performance is impaired and their completion time during racing increases. The present authors examined whether changing internal states in a way that also restricts eye movements reduces coordination and affects performance. Participants (N = 24) completed a simulated rally stage under manipulation of their anxiety state through ego threat. Performance decreased under pressure, and the decrement was associated with a narrowing of the range of eye movements and a reduced correlation of eye movements with steering. The authors discuss the possibility that the deterioration in performance is a cost of maintaining steering when eye-movement driving input to the steering controller is reduced.

When approaching a bend in the road, a driver looks across to the inside kerb before turning the steering wheel. Eye movements and steering are tightly linked, with the eyes leading, which means that the oculomotor controller can assist the neural centres controlling steering. This optimum coordination is observed for all drivers; but despite being the preferred solution to the motor-control problem of successfully steering along a winding road, the question remains as to how crucial such coordinated eye and steering movements are for driving performance. Twenty subjects repeatedly drove a simulated stage of the World Rally Championship, aiming to complete the course in the fastest possible time. For the first six repetitions they used the usual coordination of eye movements and steering; for drives 7--12 they were instructed to fixate on a small spot in the centre of the screen (centre gaze). Prevention of coordination in this way impaired their performance (drives 6 and 7 compared), dramatically increasing their time taken to complete the course, equivalent to slipping 19 places down the leader board in the actual rally stage. This indicates that the usual pattern of eye movements correlated with steering is crucial for driving performance. Further experiments are suggested to reveal whether any attentional demand associated with keeping the eyes still contributes to the loss in performance.